I am sure Microsfoft will fix this soon. Software updates are tough because user environments differ so much.
Microsoft has quarterly revenues of over $23 Billion.
User environments are diverse .... but Microsoft can afford to replicate many different environments when testing their fixes.
If Microsoft thoroughly tested KB3004394, then how could they miss the many many many problems that users are reporting in this (and other) threads.
And this is not the first time that a fix was released that caused massive problems. It seems that EVERY MONTH, one or more of the fixes causes severe customer problems.
It appears that Microsoft needs to significantly improve their fix testing procedures.